Process for producing finely-granulated compounds



Patented July 14, 1925.

UNITED STATES ADOLF WELTER, OF KREFELD-RHEINHAFEN, GERMANY.

PROCESS FOR PRODUCING 'FINELY-GRANULATED COMPOUNDS.

No Drawing.

To all whom it may concern:

Be it known that I, ADOLF WELTER, citizen of the German Empire, residing at Krefeld-Rheinhafen, Germany, have invented newand useful Improvements in Processes for Producing Finely-Granulated Comounds, of which the following is a specication.

.A process described by me in a previous patent application Serial No. 395,076, filed July 9, 1920, for the production of sodium carbonate containing water of crystallization, or of mixtures thereof, with other substances, .consists in steam, water, snow, or hydrous solutions of soap, Glaubers salt, or water-glass being sprayed upon commercial pulverized calcined sodium carbonate or mixtures thereof and in preventing liquefaction or caking by keeping the sodium carbonate in motion, whllst preferably also cooling the same.

I have found that my afore-mentioned process is capable of a general application,

inasmuch as sodium carbonate containing water of crystallization or mixtures thereof are not the onlyproducts that can be made by it. It may also be employed for converting other salts into fine crystalline subcess consists in using it for enveloping oxidizing and reducing agents, which are liable to be affected by the weather or atalyzers, with stabilizers. In using the process it is .not necessary to employ apparatus made of metal, as the towers may be made of wood and the nozzles of glass or other suitable materials. In consequence it is precluded that undesired metallic particles or oxides, in particular iron oxide can enter into combination with the chemicals being treated.

' Such metallic particles or oxides in' the presence of sensitive materials being treated might easily exert a catalytic effect and cause decomposition, or such metallic particles'or oxides might alternately oxidize and reduce each other by absorbing oxygen from the air and delivering the same to the chemicals. This is avoided by the' present Application filed August 13, 1920. Serial No. 403,418.

process. Another advantage oflered by the process 1s that if the fine division of particles is maintained during the whole pro cess, it is possible to use lower temperatures than hitherto in drying operations, on. ac- I tageous manner of carrying out such processes consists in introducing the liquid that 1s to be inspissated in a finely divided form into the upper part of a tower, and in mixmg fine particles of solid substances with the moist vapor thus formed by suction or compressed air, or by mechanical contrivances, and by finally directing air of a lowered or an increased pressureagainst the falling moistened particles so that the substance arrives at the bottom in a dry and non-caked condition. I

To carry out the process in this latter form the particular 1i ui'd which is a solvent for the substance to e treated is sprayed in the finest possible particles in-the upper part of a tower of any desired material, it'

being of no consequence how this is done, or whether the spraying device itself is. inside or outside of the tower. The fine solid particles that are adapted for absorbing the nebulous spray are then pressed or sucked into the upper part of the tower through lateral holes in the same, or these particles are made to form a dust cloud by mechanical means, when a thorough moistening and an exceedingly great surface formation will occur. The solid moistened particles will now drop down in the tower. On their way to the bottom they will bar thoroughly dried by the current of air sucked or. pressed through the tower, so that they now will not cake. If the air drawnfor pressed out of the top of the tower, should still con tain small floating solid particles,'these-can easily be separated by any preferred kind of filtering devices.

This form of the process permits of very used for dessicating may be very low, which is a great advantage in treating bodies which are easily decomposed. This form of the process is also adapted for continuous working and is very economical. The drying 0 eration can be combined with a number 0 others such as the colouring, impregnating, sugaring, disinfecting or sterilizing .of the particular pulverized raw stufi's or substances used.

Ewamples.

1. Crystalline erborate of sodium is sucked or blown into the upper part of a wooden tower of a height of about 30 feet and about '7 to-9 feet in diameter and water-glass solutions of about 30 to 40 B. are squirted through fine spraying nozzles onto the perborate cloud. For better supervision lass windows are provided in the tower. he air current produced in the tower by suction or pressure soon causes the water to evaporate and the particles of perborate coated with a protecting layer of Waterglass drop without caking to the bottom of the tower, or the small quantity of them ,that are carried away by the dessicating current of air can be separated from it by dust chambers. In this way a perborate of sodium powder is obtained each granule of which is coated with a protective layer, and which will keep for an indefinite period. But if perborate of sodium were mixed with a water-glass solution in the ordinary way, a hydrous crystalline paste would result which, before long, will become stifl. It is exceedingly difiicult to dry this crystalline paste well enough to render it capable of being ground, even if it is previously broken into fra ments. Iron mills would be required for the grinding operation and hence iron would be absorbed which would act as a catalyzer and assist in decomposing the perborate. In the aforedescribed novel process, however, not the slightest amount of oxygen is lost and no iron whatever enters the product. H 2. A cloud of fine anhydrous sodium sulfate dust is produced in the upper part of tower built of iron but which, in other respects, is similar to that described in 1. Water is also introduced through a nozzle in the pper part of the tower in a fine spray. he said dust is thus evenly moistened and at the same time it becomes so heavy that it nearly all sinks to the bottom, where it accumulates in the form of fine hydrous crystals of Glaubers salt. Only small quantities of the salt dust are carried along by the air current, which is drawn from the upper part of the tower by a suction device so that the provision of a dust chamber at this part is generally unnecesaway through the sieve in any suitable manner.

a dust cloud of coal-tar dyes melted together with dextrineand afterwards pul-.

verized is formed and sprayed with wood alcohol or ethyl alcohol. The powder dries almost immediately and its unpleasant appearance is changed by its being converte into small shining cantharidian crystals.

I claim:

3. In a tower of the kind described in 2 I den 1. A process for coating finely divided compounds, consisting in spraying fine particles of liquid on fine particles of a solid substance falling downward in a reaction chamber, and subjecting the liquid upon each of said fine particles to evaporation in a current of air.

2. The process. of acting upon a solid finely divided substance with a spray of a substance which is a solvent for the solid substance, said process comprising keeping the finely divided substance after its being sprayed upon moving in a downward direction against a current of air thereby evaporating the solvent sprayed upon the fine particles of the granulated substance 3. A process for forming coatings upon finely divided substances, consisting in spraying the enveloping substance in a 'solution upon the finely divided solid substance to be coated falling downward in a reaction chamber, and drying each particle of the same while said articles are suspended in the form of a ust cloud thereby evaporating the solvent from said solution.

4. A process for forming coatings on finely divided solid substances by the action of a finely divided solvent of saidsolid substance, consisting in spra g the solvent in finely divided liquid particles onto the finely divided solid substance falling. downward in a reaction chamber, and removing said solvent while said finely divided substance is floating in the form of a dust cloud.

5. A process for rendering solid substances stable, consisting in spraying onto the pulverized solid substance fallin downward in a reaction chamber, a staiilizing substance dissolved in a solvent for the pulverized solid substance, drying the solid substance by keeping the same moving during the spraying operation so as to prevent its liquefaction or' caking and evaporating said solvent.

6. A process of protecting easily decomposable salts which comprises spraying the solid particles of said salts falling downward in a reaction chamber with a solution of a protective substance, and evaporating .formed on theparticles while said particles are suspended in a gas.

7. A process which consists in introducing a liquid in a finely divided form into the upper part of a treating chamber, mixing finely divided particles of a solid substance with the finely divided liquid particles, and directing air against the falling moistened particles to evaporate at least some of said liquid.

.8. A process of treating finely divided solid substances which consists in introducing liquid which is a solvent for the solid substance into the upper part of a treating chamber in finely divided condition, introducing into said chamber finely divided particles of said solid substance so as to be acted upon by the finely divided liquid, and drying the moistened solid particles as they descend in the form of a cloud within said chamber.

9. A process of coating finely divided solid substances which consists in introducing the substance into a treating chamber in the form of a cloud of finely divided particles, subjecting said finely divided particles within said chamber to the action of a solution of a coating substance introduced in the form of finely divided particles, and removing the solvent from said solutionby drying so as to leave a substantially dry protective coating upon each particle of said substance.

10. A process of treating solid substances, which consists in introducing the substance in the form of a cloud of finely divided particles into the upper art of a treating chamber, introducing a liquid in the form of a fine spray into said treating chamber to act upon the finely divided particles of said solid substance, and subjecting the treated particles to the action of a current of a gaseous medium.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

' DR. ADOLF W'ELTER. Witnesses:

GUs'rAv RAUTER, Lmsn Boron. 

